Hahn, 33, ended a wild day of multiple lead changes on a difficult Riviera Country Club layout in wet and cool conditions by edging out fellow American Dustin Johnson and England's Paul Casey for the win.

Born in South Korea but educated in the United States, Hahn struck his tee shot at the third extra hole, the par-three 14th, to 24 feet and coolly sank the birdie putt before the long-hitting Johnson missed his attempt from 12 feet.

Casey was eliminated on the previous hole, the tricky par-four 10th, where Johnson and Hahn both hit superb lob wedges from wet rough to the back left of the green and sank their birdie putts.

"This is amazing," an emotional Hahn told CBS Sports. "I have a little girl coming in three weeks and I never would have thought I would win this golf tournament with so many great players here.

"I'm more excited about being a dad than winning any golf tournament," he said shortly before the playoff. "After today, I'm going to fly back home and spend some time with my wife.

"Pick up some money here, which is always nice, and be able to buy a lot of diapers the next couple weeks."

The trio had finished the 72 regulation holes on six-under-par 278, Johnson and Hahn each closing with a two-under 69 and Casey finishing bogey-birdie-birdie-bogey for a 68.

Spaniard Sergio Garcia had been a stroke in front with two holes to play but bogeyed 17 and 18 for a 71 and a tie for fourth at five under with Americans Jordan Spieth (70) and Keegan Bradley (68) and Japan's Hideki Matsuyama (67).

"I didn't deserve to win this week, it's as simple as that," Garcia said. "It caught up with me on the last, six, seven holes. It was already a good effort for me to have a chance."

Overnight leader Retief Goosen birdied the par-five first to briefly maintain his two-stroke cushion but his round then unravelled after he bogeyed the short fourth.

The veteran South African, seeking his first PGA Tour win since the 2009, closed with a 75 that included double-bogeys at the eighth and 13th to finish in a tie for eighth.

"Obviously 13 was the killer," said Goosen, a double U.S. Open winner. "I'm kicking myself, that's for sure. That was an opportunity missed."